I have two versions of LO installed.
One is 6.1.5.2 because of Debian 10 has it and it cannot be removed as it is a dependency to Gnome.
I also have 7.5.3.2 installed to use an up-to-date version.
The two together has some small, but annoying issues:

POP-UP
If I use the new version for the first time, I get a pop-up window with the tip of the day and an information bar that I am using it for the first time, as I guess it is designed.
If for whatever reason (file type linking to application not changed everywhere to the new version, is the prime reason) I open the older version of LO (not necessarily Calc, it can be e.g. Writer as well), next time when I use the newer version, I get again the annoying pop-ups. I could not find a way to make it "know" that I already use it.

TWO VERSION PARALLEL
If I have the older version open and try to open at the same time the newer version, either using the favorites fast menu or the full list of applications, I get still another copy of the old version. If I use the favorites quick menu, the mouse hint pulling it over the icon even says 7.5, but it still loads the old version. Similarly, when I use the full application menu, the name of the icon is Calc 7.5, but runs the old version.
The opposite direction, i.e. first opening the new and then the old is the same thing, i.e. I get a second copy of the new instead of the old.
What is also strange that if I only open the new from the favorites menu, (what I have listed there, but the old one is not!), instead of getting it marked as an active application (blue underscore of the icon in my set-up), I get back the old icon in the favorites menu and THAT is marked as active.
It seems that the two versions cannot be started at the same time.

OPENING A SECOND DOCUMENT
However, from the above it seems that the two application launcher icons are very closely linked, it is not entirely the case.
1. If I open a new spreadsheet with the new SW version from the favorites bar and do not touch it and try to open a second, regardless if I do it (a) from the favorites bar with the new icon, (b) from the favorites bar with the just appeared (see above) old icon, (c) from the full application list with the new icon or (d) with the old icon, I always get an Untitled2. Still, this is not entirely the same. If the second is also opened with a new icon (either from the favorites (a) or from the full list (c)), in the favorites the new icon gets marked as active as well. If I open it with the old icon ((b) or (d) from above), then still only the old icon remains marked.
2. If I open a new spreadsheet (no other open LO window before!) from the full list of applications with the new icon and then try to open a second one (again, without touching the first one), 3 out of 4 I get a new Untitled2, except if I try to open it again from the full list of application with the new icon, because in this case it does not open a new document, just brings the first one forward.
3. If I open a new spreadsheet from the full list of applications with the old icon and then try to open a second one, the opposite happens. 3 out of 4 I do not get a new document. The only exception if I use the favorites bar, NEW icon, in which case I get an Untitled2 but again, as said above with the OLD software.

These are just annoying little things, this is why I put it minor. Maybe some of it is not even LO but Gnome/gtk3 related, I do not know.
Also, this whole things would go away, if I could change in Gnome the dependency to the new version and could remove the old version completely.